Around town

警察 (jǐng chá), 警官 (jǐng guān) and 警方 (jǐng fāng) are all the police, and the first character is the giveaway.

警 (jǐng) is to warn or to alert. Then:

警察 is a police officer, the ordinary word for the person. 警官 adds 官 (guān), an official, and is the respectful form of address. 警方 adds 方 (fāng), a side or party, and means the police AS AN INSTITUTION - the word a news report uses.

You do not need to memorise three words. You need to recognise 警 and then read the second character, which is doing the specifying. That is how a great deal of Mandarin vocabulary works once you are past the first thousand words.

家 turns up again

家 (jiā) was family and home in the chapter-8 session. Here it is inside 国家 (guó jiā), a country, literally a state-household.

That is not a poetic flourish. It is how the word was built, and the metaphor of the nation as an extended family runs deep enough in Chinese political language to be worth noticing rather than skipping.

Roads and streets

路 (lù) is a road. 街 (jiē) is a street, more urban and usually with shops on it.

路上 (lù shàng) is on the way, in transit. The 上 is literally on top of, and Mandarin uses these position words far more systematically than English does: 上 for on, 里 for in, 下 for under, all placed AFTER the noun rather than before it.

房子 and 房间

房子 (fáng zi) is a house, the building. 房间 (fáng jiān) is a room inside one. The 间 is the same character used as a measure word for rooms, and it originally meant the space between things.

Compare 时间 from the time session: the space between moments. One character, two useful words, and a metaphor that holds in both.